Please be advised that if you keep them, you will have to clean the bowl more often. A lot of people have the misconception that snails will 'clean' the tank, when in fact all they are doing is turning algae and food into poo. If you've seen how slow they move, you'll know that they don't exactly burn all those calories that they eat!

Imo they would all get along great in a 3 gallon tank with some filtration and heat... maybe even a java fern or two to soak up that extra waste-- You should check into it!